Dual hydraulic hospital bed with emergency bypass circuit

Abstract

A hydraulically operated hospital bed with dual hydraulic power systems for operation with or without electrical service. The bed has its head and thigh/leg elevation functions performed by hydraulic cylinders. A control circuit meters the introduction and removal of hydraulic fluid from these cylinders so an occupant of the bed is not subjected to any sudden movement. In case of an emergency requiring the bed occupant to be in a supine position (the need to perform CPR), the normal control circuit is bypassed by an emergency circuit that allows much faster than normal lowering of the head and thigh/leg portions of the bed.

What is claimed is: 
     
       1. In combination with a hospital bed of the type having a generally rigid platform which has attached to it movable patient supporting surfaces, said movable patient supporting surfaces being movable from a generally horizontal position to an elevated position and including head, thigh and leg portions, an improved hydraulic system including: A. A plurality of hydraulic cylinders having extensible and retractable operating rodsad having said operating rods connected to said head, leg and thigh portions, whereby movement of said operating rods will move said head, leg and thigh portions;   B. A source of hydraulic fluid under pressure connected to said hydraulic cylinders, said source of hydraulic fluid under pressure comprising a dual power source which can be an electrically driven pump and a manually operated foot pump;   C. A reservoir for said hydraulic fluid, said reservoir being at substantially atmospheric pressure;   D. Control valve means, connected in circuit intermediate said source of hydraulic fluid under pressure, said reservoir, and said hydraulic cylinders, selectively operable to direct hydraulic operating fluid to and from selected hydraulic cylinders to extend and retract said operating rods said control valve means comprising; i. a normally closed, electrically operated extension valve connected between each of said hydraulic cylinders and said electric pump;   ii. a normally closed, electrically operated retraction valve connected between each of said hydraulic cylinders and said reservoir;   iii. a manual selector valve, connected betwen said cylinders and said manually operated pump, being operable to direct hydraulic fluid from said manually operated pump to any one of said hydraulic cylinders;   iv. a normally closed, manually operated dump valve, connected to said manual selector valve and said reservoir, whereby opening of said dump valve will cause said cylinder that is connected to said manual selector valve to return the hydraulic fluid in it to said reservoir; and     E. Emergency bypass hydraulic circuit means for draining hydraulic fluid from said cylinders to said reservoir without use of said control valve means to thereby allow faster retraction of said operating rods and consequent faster lowering of said head, thigh and leg portions than is allowed by said control valve means.   
     
     
       2. The combination of claim 1 wherein said head portion is operated by two hydraulic cylinders which operates as a unit and are controlled by a single extension valve and a single retraction valve. 
     
     
       3. The combination of claim 1 which further includes: A. A hydraulic elevation cylinder having an extensible and retractable operating rod connected to said rigid platform;   B. A base frame to which said hydraulic elevation cylinder is attached; and   C. Second control valve means, connected in circuit intermediate said source of hydraulic fluid under pressure, said reservoir and said hydraulic elevation cylinder, selectively operable to direct hydraulic fluid to and from said hydraulic elevation cylinder to thereby raise and lower said rigid platform, said second control valve means being connected such that it will not allow hydraulic fluid to flow through said emergency bypass hydraulic circuit means, thereby maintaining said rigid platform at its chosen elevation when said emergency hydraulic circuit means is activated.   
     
     
       4. The combination of claim 1 wherein said emergency bypass hydraulic circuit includes: A. A normally closed, manually operated emergency valve, connected in circuit to all of said hydraulic cylinders and to said reservoir and bypassing said control valve means; and   B. A one way check valve, connected in circuit intermediate each of said hydraulic cylinders and said emergency valve and positioned to allow hydraulic fluid flow only away from said hydraulic cylinders.